1-First, soften the butter at room temperature for about 30 minutes; this helps create an airy texture that’s easy to work with.

2-Next, in a mixing bowl, beat the softened butter on medium speed until it’s creamy, which takes around two minutes to build a smooth base.

3-Then, add the powdered sugar gradually, one cup at a time, and beat well after each addition to avoid any lumps forming.

4-After that, mix in the blueberry powder or jam along with the vanilla extract, adjusting amounts if you want a stronger blueberry vanilla cake buttercream flavor.

5-Slowly incorporate the heavy cream or milk to get the right consistency, making sure it’s spreadable and not too thick.

6-For substitutions like vegan options, swap in plant-based ingredients and blend thoroughly before chilling the buttercream for 15 minutes.

7-This final step lets it set nicely, so it’s ready to spread on your cake without losing shape.